Taylor Lynn-Marie Beard1, Kristy Borrelli2, Amanda McClellan Maaz1, Canming Xiao3 and William L Pan4, (1)Crop and Soil Sciences, Washington State University, Pullman, WA (2)Washington State University, Pullman, WA (3)Washington State Department of Ecology, Yakima, WA (4)PO Box 646420, Washington State University, Pullman, WA
Arid and semi-arid agronomic regions that have adopted conservation management practices, such as reduced tillage, may be prone to soil crusting. Surface crusting is predominantly caused by the combination of raindrop impact and excessive Si in the soil. Crusting can reduce water infiltration, enhance runoff & erosion, and interfere with seed germination. Structural components (e.g. lignin and silicon (Si)) vary between crop types. Grasses such as wheat tend to have higher levels of Si and lower amounts of lignin when compared to oilseeds. When such residue is left on the soil surface these components, specifically Si, may contribute to soil crusting. The main goal of this research is to understand the potential of canola and wheat residues to resist degradation and impact soil crusting. In order to compare the effects of rotation history, a soil incubation was conducted with two soil types. The first soil was collected from a field traditionally grown in a winter wheat-fallow rotation and the second soil was collected from a spring canola-fallow rotation. Initial values of soil Si were higher in the soil collected from the wheat field (1851.9 mg Si/kg soil) when compared to the canola field (1418.2 mg Si/kg soil). Three rates of silica solution (SiO2), representative of amounts that would be found in wheat and canola residues, were added to each soil type. The treatment with the highest amount of Si solution combined with the soil previously cropped in wheat had a positive effect on soil crust thickness (25.3 mm) and a significant effect on surface resistance (0.74 kg/cm2). Therefore, it may be beneficial to consider crops with lower amounts of Si when planning crop rotations in areas where soil crusting can be a concern. Further research on this topic will include conducting a field survey on comparable fields this summer.